Hi !
While changing an active sentence in to passive, the object of the active sentence will become the subject of the passive sentence and the new object is preceded by the preposition 'by' Passive often is used in description of processes and scientific experiments. Activity: change the verbs in brackets in to a suitable passive forms
The liver receives blood full of digested food from the gut. Any food which isn't immediately needed by the cells is taken to the liver where it is stored. The liver contains enzymes which help it to perform a variety of functions. Excess Proteins are broken down to release a waste production called Urea which is taken to Kidneys. The Urea is excreted in the Urine poisons such as alcohol and medicines are also removed by the liver.
Hope it helps :)